None.
Not Applicable.
The present invention relates to vehicle wheel alignment, and more particularly to vehicle wheel alignment systems which embody movable video cameras and wheel mounted optical targets.
Two such vehicle wheel alignment systems are presently available in the marketplace. One, sold by Hunter Engineering Company and labeled as the DSP-400(trademark), is generally described by U.S. Pat. Nos. 5,675,515, 5,870,315, 5,724,128, and 6,064,750. The other vehicle wheel alignment system, sold by Industrial Diagnostics Selling Co. (IDSC) under the trade name John Bean, and labeled as the Visualiner 3D(trademark), is generally described by U.S. Pat Nos. 5,535,522, 5,724,743, 5,809,658, and 5,943,783.
These systems operate by using video cameras to generate video images of optical targets which are mounted to the wheels of a vehicle. These video images may be in either analog or digital format. Computers are then used to measure the generated images and relate the measurements obtained thereby to corresponding known information about the optical targets. This allows the positions and orientations of the optical targets to be computed, from which the alignment angles of the wheels of the vehicle are computed.
The design of such a system involves tradeoffs, as does the design of any wheel alignment system. One such tradeoff is between focal length and vertical movement of the vehicle lift rack. It is desirable to make the focal lengths of the cameras short enough that the wheel mounted optical targets are in the fields of view of the cameras when the vehicle lift rack is raised to allow the technician to work under the vehicle. In general, the desired working height of the lift rack can be anywhere from xe2x80x9call the way downxe2x80x9d to xe2x80x9call the way upxe2x80x9d, which is a range of some six feet or so in height. If the focal lengths of the cameras are made short enough to accomplish this, the targets appear so small in the image that measurement of the image becomes difficult and inaccurate, if not actually impossible. The tradeoff is to make the focal length as long as is necessary for the required accuracy and accept the limited range of movement for the vehicle lift rack which this imposes. The result is that measurements of the vehicle wheel alignment can be made only with the vehicle lift rack in a smaller range of vertical positions such that the cameras can view the targets and measure the images produced, and this range of vertical positions is generally smaller than desired. The system must be very accurate to be of commercial use, and achieving the required accuracy is quite difficult, therefore achieving the required accuracy wins the tradeoff and the vehicle wheel alignment can be measured with the vehicle lift rack in only a limited range of vertical positions.
This can be made easier by using a video camera design which embodies CCD detectors having a larger number of pixels. For example, instead of using a CCD detector having pixels in a 640xc3x97480 format, one could use a 2000xc3x971000 format. Unfortunately, such CCD detectors are currently much too expensive for use in such a system. Further, using such a design places extreme demands on the quality of the lenses used by the video cameras, thereby further increasing their costs. Such a solution, while possible, is not currently economically practical.
One solution to this problem is to mount the cameras to a mechanism which pivots so as to allow the cameras to point more downward when the vehicle lift rack is in a lower position, and more upward when the vehicle lift rack is in a higher position. While possible, this is not very practical due to the wide range of sizes of vehicles which such a system must be capable of measuring, and due to the wide range of orientations of the targets relative to the cameras.
A practical solution to this problem is to design the system such that the cameras can be raised up or down to match the corresponding change in height of the vehicle lift rack. Such a system is described in U.S. Pat. Nos. 5,675,515 and 5,870,315, the full disclosures of which are incorporated herein by reference.
The Visualiner 3D(trademark), as sold by IDSC, optionally embodies such a design. In the Visualiner 3D(trademark) version, a vertical post is mounted to the floor. A horizontal beam is mounted to a traveler which is free to move vertically along this vertical post. The video cameras are mounted to the ends of the horizontal beam such that they are aimed generally down the sides of the vehicle and can see the targets mounted to the vehicle wheels. A counterweight inside the vertical post is connected by cables to the traveler such that the traveler and horizontal beam can be raised or lowered to any desired position, thereby allowing the cameras to be positioned to work with any height of the vehicle lift rack.
In the Visualiner 3D(trademark) version, a conventional chain-and-cable type garage door opener is used to provide the motive force to move the horizontal beam and control its position. The garage door opener is mounted with the motor above the vertical post and the boom of the opener textending down inside it. The traveler of the garage door opener is connected by a cable to the traveler of the horizontal beam, such that the garage door opener provides both the motive force to move the cameras up or down and the operating controls to allow the technician to move the cameras and stop at a desired position.
This garage door opener operates exactly as it would if it were connected to a garage door. If the alignment technician presses and releases the control pushbutton, the cameras move up or down, whichever is the opposite of the direction they last moved. If then left alone, the cameras move until a built in limit switch trips, at which point the cameras stop moving. If the technician presses the pushbutton while the cameras are moving, the response depends on the direction of movementxe2x80x94if the movement is up, the cameras stop moving; if the movement is down, the cameras reverse direction and move up, exactly as would a garage door. This means that the technician can stop the cameras at a desired position only when the cameras are moving up, unless the desired position is where a limit switch stops the movement.
While functional, the Visualiner 3D(trademark) camera lift mechanism is clumsy to use. The technician is able to stop the cameras at a desired vertical position only when the cameras are moving up. If the cameras are moving down, pressing the pushbutton causes them to reverse direction and move up. This can make small adjustments in the camera position difficult and clumsy to accomplish. The lift mechanism moves the cameras up or down rather quickly, which some might call an advantage, but it makes stopping the cameras at a precise location very difficult, as there is a noticeable lag between the pushing the pushbutton and the cameras stopping. A remote control is available (a conventional garage door remote control), but using it is even more difficult, as there is about a one second lag in time between when the button is pushed and the motor responds, which is longer than with the conventional pushbutton.
There exists a clear need for apparatus and methods which allow easy and simple control of a camera positioning system to move the cameras to a desired position.
Among the various objects and features of the present invention may be noted the provision of improved apparatus and method for controlling the position of video cameras in a wheel alignment system embodying a camera positioning system.
Briefly, the apparatus of the present invention includes optical targets for mounting to the wheels of a vehicle, at least one video camera for viewing said optical targets and producing at least one image thereof, and a computer system for measuring said at least one image and for using the measurements to compute vehicle wheel alignment information. A positioning system is included for positioning the at least one video camera such that the optical targets are visible to the at least one video camera and such that it can produce the image of said targets. A controller is further included for controlling the positioning system such that a user of said apparatus can cause the at least one video camera to be positioned in at least one desired position. The controller is further configured such that the user can direct the controller to store or xe2x80x9crememberxe2x80x9d the at least one desired position, and such that any user can, at a later time, direct the controller to recall the stored position and move the at least one video camera to the stored position.
Briefly, the method of the present invention for controlling camera position in a wheel alignment system having optical targets mounted to the wheels of a vehicle, at least one video camera configured for viewing said optical targets and producing at least one image thereof, a computer system configured for measuring said at least one image and for using said measurements to compute vehicle wheel alignment information, and a positioning system configured for positioning said at least one video camera such that said at least one video camera can produce said at least one image of said targets is described. The method comprises the steps of positioning the at least one video camera in at least one desired position, and storing the at least one desired position in a controller such that a user can, at a later time, cause said controller to recall said stored position and cause the positioning system to position the at least one video camera at the stored position.
Briefly, a further method of the present invention is that in response to a desired position being identified by a user, the camera positioning system be controlled to cause the at least one video camera to move to the identified position.
The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings.